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(#) WebViews in wrap_content parents

!!! ERROR: WebViews in wrap_content parents
   This is an error.

Id
:   `WebViewLayout`
Summary
:   WebViews in wrap_content parents
Severity
:   Error
Category
:   Correctness
Platform
:   Android
Vendor
:   Android Open Source Project
Feedback
:   https://issuetracker.google.com/issues/new?component=192708
Since
:   Initial
Affects
:   Resource files
Editing
:   This check runs on the fly in the IDE editor
Implementation
:   [Source Code](https://cs.android.com/android-studio/platform/tools/base/+/mirror-goog-studio-main:lint/libs/lint-checks/src/main/java/com/android/tools/lint/checks/WebViewDetector.java)
Tests
:   [Source Code](https://cs.android.com/android-studio/platform/tools/base/+/mirror-goog-studio-main:lint/libs/lint-tests/src/test/java/com/android/tools/lint/checks/WebViewDetectorTest.kt)
Copyright Year
:   2014

The WebView implementation has certain performance optimizations which
will not work correctly if the parent view is using `wrap_content`
rather than `match_parent`. This can lead to subtle UI bugs.

(##) Example

Here is an example of lint warnings produced by this check:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~text
res/layout/webview.xml:18:Error: Placing a <WebView> in a parent element
that uses a wrap_content layout_height can lead to subtle bugs; use
match_parent instead [WebViewLayout]
    &lt;WebView
     -------
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Here is the source file referenced above:

`res/layout/webview.xml`:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~xml linenumbers
&lt;LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent"&gt;

    &lt;!-- OK --&gt;
    &lt;WebView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" /&gt;

    &lt;LinearLayout
        android:orientation="vertical"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"&gt;

        &lt;!-- Report error that parent height is wrap_content --&gt;
        &lt;WebView
            android:layout_width="match_parent"
            android:layout_height="match_parent" /&gt;

        &lt;!-- Suppressed --&gt;
        &lt;WebView
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            tools:ignore="WebViewLayout" /&gt;
    &lt;/LinearLayout&gt;

&lt;/LinearLayout&gt;
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

You can also visit the
[source code](https://cs.android.com/android-studio/platform/tools/base/+/mirror-goog-studio-main:lint/libs/lint-tests/src/test/java/com/android/tools/lint/checks/WebViewDetectorTest.kt)
for the unit tests for this check to see additional scenarios.

The above example was automatically extracted from the first unit test
found for this lint check, `WebViewDetector.testMatchParentWidth`.
To report a problem with this extracted sample, visit
https://issuetracker.google.com/issues/new?component=192708.

(##) Suppressing

You can suppress false positives using one of the following mechanisms:

* Adding the suppression attribute `tools:ignore="WebViewLayout"` on
  the problematic XML element (or one of its enclosing elements). You
  may also need to add the following namespace declaration on the root
  element in the XML file if it's not already there:
  `xmlns:tools="http://schemas.android.com/tools"`.

  ```xml
  &lt;?xml version="1.0" encoding="UTF-8"?&gt;
  &lt;WebView xmlns:tools="http://schemas.android.com/tools"
      tools:ignore="WebViewLayout" ...&gt;
    ...
  &lt;/WebView&gt;
  ```

* Using a special `lint.xml` file in the source tree which turns off
  the check in that folder and any sub folder. A simple file might look
  like this:
  ```xml
  &lt;?xml version="1.0" encoding="UTF-8"?&gt;
  &lt;lint&gt;
      &lt;issue id="WebViewLayout" severity="ignore" /&gt;
  &lt;/lint&gt;
  ```
  Instead of `ignore` you can also change the severity here, for
  example from `error` to `warning`. You can find additional
  documentation on how to filter issues by path, regular expression and
  so on
  [here](https://googlesamples.github.io/android-custom-lint-rules/usage/lintxml.md.html).

* In Gradle projects, using the DSL syntax to configure lint. For
  example, you can use something like
  ```gradle
  lintOptions {
      disable 'WebViewLayout'
  }
  ```
  In Android projects this should be nested inside an `android { }`
  block.

* For manual invocations of `lint`, using the `--ignore` flag:
  ```
  $ lint --ignore WebViewLayout ...`
  ```

* Last, but not least, using baselines, as discussed
  [here](https://googlesamples.github.io/android-custom-lint-rules/usage/baselines.md.html).

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